The investigator proposes to continue studies on the following aspects of myocardial metabolism: (1) Regulation of fatty acid oxidation by heart mitochondria, including continued studies on the role of carnitine, competition by other metabolites, etc. (2) Evaluation of the presence and importance of a mechanism for oxidation of unsaturated fatty acids involving combined Beta-oxidation and gamma-oxidation. This latter type of oxidation yields propionate, which can be converted to succinate via methylmalonate and requires both biotin and cobamide coenzyme systems. (3) Role of fatty acids in the contractile activity of beating heart cells from adult mammals.